Effects of High-Fat Diet at Two Energetic Levels on Fecal Microbiota, Colonic Barrier, and Metabolic Parameters in Dogs

Abstract

Increased consumption of energy-rich foods is a key factor in overweight, obesity, and associated metabolic disorders. This would be, at least in part, related to microbiota disturbance. In rodent models of obesity, microbiota disruption has been associated with alteration of the intestinal barrier, endotoxemia, inflammation grade, and insulin sensitivity. The aim of the present study was to assess the effects of a high-fat diet (HFD), fed at two energetic levels, on microbiota, intestinal barrier, and inflammatory and metabolic parameters in dogs. A HFD (33% fat as fed, 4,830 kcal/kg) was given to 24 healthy Beagle dogs at 100% (HF-100; n = 8) and at 150% (HF-150; n = 16) of their maintenance energy requirements for 8 weeks. Analysis of similarity revealed a significant difference in gut microbiota β-diversity following the diet compared to week 0 in both groups while α-diversity was lower only in the HF-150 group. Firmicutes/Bacteroidetes ratio was higher in the HF-150 group compared to the HF-100 group at weeks 2 and 8. A reduction in insulin sensitivity was observed over time in the HF150 group. Neither endotoxemia nor inflammation was observed in either group, did not find supporting data for the hypothesis that the microbiota is involved in the decline of insulin sensitivity through metabolic endotoxemia and low-grade inflammation. Colonic permeability was increased at week 4 in both groups and returned to initial levels at week 8, and was associated with modifications to the expression of genes involved in colonic barrier function. The increase in intestinal permeability may have been caused by the altered intestinal microbiota and increased expression of genes encoding tight junction proteins might indicate a compensatory mechanism to restore normal permeability. Although simultaneous changes to the microbiota, barrier permeability, inflammatory, and metabolic status have not been observed, such a causal link cannot be excluded in dogs overfed on a HFD. Further studies are necessary to better understand the link between HFD, intestinal microbiota and the host.

Keywords: colonic barrier; dog; high-fat diet (HFD); insulin sensitivity; microbiota (microorganism).

Figure 1

Experimental design of the study. HF-100 corresponds to the group of dogs fed the high-fat diet at 100% of maintenance energy requirement and HF-150 corresponds to the group of dogs fed the high-fat diet at 150% of maintenance energy requirement. HF-150a and HF-150b are two separate subgroups consisting of 8 dogs from the HF-150 group.

Figure 2

(A) Body weight and (B) Body condition score (BCS) in dogs fed the high-fat diet at maintenance (HF-100; n = 8) and at 150% maintenance (HF-150; n = 16) during 8 weeks. Data are mean ± SEM. ****P < 0.0001 for the HF-150 diet vs. week 0, ^$P < 0.05, ^$P < 0.01, ^$$$P < 0.001 HF-150 vs. HF-100 at the same week.

Figure 3

(A) The β-diversity, the indices of (B) OTUs, (C) Chao1 and (D) Shannon, (E) relative abundance of bacterial on phyla level and (F) Firmicutes/Bacteroidetes ratio found in fecal samples of dogs fed the high-fat diet at maintenance (HF-100; n = 8) and at 150% maintenance (HF-150; n = 16) for 8 weeks. Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 during the HF-150 diet vs. week 0, ^$P < 0.05 HF-150 vs. HF-100 at weeks 2 and 8.

Figure 4

Relative abundance of the fecal bacterial groups belonging to the phyla Firmicutes [(A) Clostridia, (B) Clostridiales, (C) Clostridiaceae, (D) Lachnospiraceae, (E) Clostridium, and (F) Ruminococcus] and Fusobacteria [(G) Fusobacteriaceae and (H) Fusobacterium] in dogs fed the high-fat diet at maintenance (HF-100; n = 8) and at 150% maintenance (HF-150; n = 16) for 8 weeks. Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 during the HF-150 diet vs. week 0, ^#P < 0.05 at week 2 vs. week 0 for HF-100 group, ^$P < 0.05, ^$$P < 0.01 HF-150 vs. HF-100 at weeks 0 and 2.

Figure 5

Relative abundance of the fecal bacterial groups belonging to the phylum Bacteroidetes [(A) Bacteroidia, (B) Bacteroidales, (C) S24_7, (D) Prevotellacaea, (E) Rikenellaceae, (F) Prevotella, and (G) Prevotella Copri] and Proteobacteria [(H) Sutterella] in dogs fed the high-fat diet at maintenance (HF-100; n = 8) and at 150% maintenance (HF-150; n = 16) for 8 weeks. Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 during the HF-150 diet vs. week 0, ^#P < 0.05, ^##P < 0.01 at week 2, 4, and 6 vs. week 0 for HF-100 group, ^$P < 0.05, ^$$P < 0.01 HF-150 vs. HF-100 at weeks 0, 2, and 4.

Figure 6

(A) Lactulose:sucralose ratio in urine after an oral administration and (B) Syndecan, (C) Claudin-2, (D) ZO-1, (E) Junctional adhesion molecule 1 (JAM1), (F) Myosin light-chain kinase (MLCK), (G) Claudin-1, and (H) Occludin mRNA levels in dogs fed the high-fat diet at maintenance (HF-100; n = 8) and at 150% maintenance (HF-150; n = 16) for 8 weeks. Data are median (range min-max). *P < 0.05, **P < 0.01, ***P < 0.001 at weeks 4 and 8 vs. week 0 for HF-150 group, ^§P < 0.05 at week 8 vs. week 4 for HF-150 group, ^#P < 0.05 at weeks 4 and 8 vs. week 0 for HF-100 group.

Figure 7

(A) Plasma glucose, (C) Plasma insulin (E), and Plasma NEFA concentrations, and the respective areas under the curves (B,D,F) during a feed-challenge test in dogs fed the high-fat diet at maintenance (HF-100; n = 8) or at 150% maintenance (HF-150; n = 8) for 8 weeks. Data are mean ± SEM or median (range min-max). ^$P < 0.05 HF-150 vs. HF-100 for the same timepoint at week 0. *P < 0.05 at week 8 vs. week 0 for HF-150 group.